Magnafloc 355 SSK Equivalent — Anionic Polyacrylamide

Two grades that are the same polymer at different granulation will give the same flocculation result once dissolved, and completely different results if one of them is not fully dissolved. That is the whole reason variants like 355 SSK exist, and it is why a substitution decision that only matches the polymer sometimes fails on site for reasons that have nothing to do with the polymer.

Fine powder wets faster and reaches full chain extension sooner, but it dusts at the hopper and forms fish-eyes — gel-coated lumps with dry powder trapped inside — if it enters the water faster than the wetting cone can disperse it. Coarse granulation solves both, and pays for it with dissolution time. A plant with a 20-minute ageing tank and coarse granulation is dosing partly dissolved polymer and paying for chain length it never gets to use.

Where this shows up in the numbers is a dose that crept upward over months with no change in feed. That pattern usually means dissolution, not the polymer. Before re-sourcing, measure the actual ageing time at working concentration and check the wetting cone for build-up, because a new supplier will not fix either.

The anionic family varies along two axes: molecular weight, which sets floc size and settling rate, and charge density, which sets how firmly the chain attaches to the particle. Most substitution errors come from matching one axis and ignoring the other. A high molecular weight, low charge grade and a high molecular weight, medium charge grade look similar on a specification sheet and behave differently on a stream with high surface charge.

The practical route is to run two charge steps side by side at your working dose. If the higher charge step gives a visibly tighter floc and clearer supernatant, your stream has charge demand and the medium position is right. If it gives a smaller, more fragile floc, you are over-charging and repulsion is working against you — step down. This test takes an afternoon and settles a question that specification sheets cannot.

Molecular weight is the easier axis to read from the outside: if your constraint is settling rate or clarifier throughput, you want the highest molecular weight your shear conditions will tolerate. If floc arrives at the clarifier broken because of a pump or a long launder, a very high molecular weight grade is the wrong answer no matter what the settling test in a quiet beaker showed.

We are an independent manufacturer with no affiliation to, endorsement from, or distribution agreement with BASF. Magnafloc is their trademark and appears here only to identify the product a buyer is looking to replace. We do not claim our product is identical to theirs, and we will not publish a numerical match against grade-level figures that are distributed through their data sheet rather than openly available.

What is testable is this: we manufacture high molecular weight anionic polyacrylamide across the low-to-medium charge band in both standard and coarse granulation, the 355 and 355 SSK positions sit inside that, and a free sample lets you run the comparison on your feed. For test methodology, the American Water Works Association documents standard jar-test practice, and the Water Environment Federation publishes solids-separation guidance useful for setting acceptance criteria before the trial rather than after it.